The disclosed embodiments of the present invention relate to wire line communication systems, and more particularly, to a line driver with active termination and an associated method.
In a conventional wire line communication system, a transmitter may need a local resistive termination with a certain value to operably match the source impedance to the channel characteristic impedance, in order to achieve maximum power transfer. When the transmitter is controlled to deliver signals to the subsequent wire line, the source impedance and load impedance will consume the same power. As a result, the efficiency of said transmitter is poor since half of the current is seized by the source impedance.
FIG. 1 is a diagram illustrating a conventional current mode DAC as a transmitter. A source impedance RS and a load impedance RL are arranged in a shunt configuration. FIG. 2 is a diagram illustrating a conventional voltage mode line driver as a transmitter. A source impedance RS and a load impedance RL are arranged in a series configuration. The amplitude of VOX is twice the amplitude of VO. For the circuits shown in FIG. 1 and FIG. 2, the source impedance RS and the load impedance RL both consume the same power.
Some alternative designs have been proposed to reduce the power dissipated on source impedance, by employing a hybrid voltage mode and a current mode driver. The obvious shortcomings of such designs are higher hardware cost and lower operational speed. Hence, there is a need for an innovative design which can solve the above mentioned issues.